The present disclosure relates to aspects of magnetic head sliders (“sliders”) within hard-disk drives (HDDs), and relates in particular to improved slider performance.
HDDs are data storage devices that include one or more rotatable disks to which data is written and read by way of one or more magnetic read/write heads that are movably supported with respect to surfaces of the disks by a like number of head suspension assemblies, which are typically movably supported relative to a respective disk surface so that a magnetic read/write head can be selectively positioned relative to a circular data track of the disk surface. Such head is typically provided on an aerodynamically-designed slider so as to fly closely, at a so-called “fly height,” of several nanometers above the disk surface while the disk is spinning. Each slider can be aerodynamically shaped to have various surfaces, including an air-bearing surface (ABS), which faces the spinning disk. The slider may also have a trailing edge (TE), which follows or “trails” the ABS with respect to the relative movement of the slider and the magnetic disk surface. Each head suspension assembly is normally connected to a rotatable drive actuator arm and load beam for rotatably moving a slider for data writing and reading during HDD operation. Sliders, as used herein (in conjunction with a spinning disk surface), may form what are referred to as advanced air bearings (AABs).
Disk surfaces have experienced increasing data density per unit area, known as areal density, as HDDs have continued to increase in storage capacity. Specifically, individual data tracks on the disk surfaces have become narrower and the radial spacing between tracks has decreased. Technologies such as heat-assisted magnetic recording (HAMR) and shingled magnetic recording (SMR) have led to greater areal density and closer-spaced data tracks. An increasing desire and need for magnetic head read/write precision in conjunction with smaller fly heights has led to greater magnetic read/write sensitivity and slider proximity to the disk surfaces.
An HDD assembly is typically a tightly-sealed structure. During assembly, an HDD is produced in an environment where minimal foreign particles and/or contaminants enter the HDD. However, contamination might get in during assembly or eventually enter an HDD, including contamination that can settle on sensitive disk or slider surfaces. Lubricant liquid and/or droplets may also be present on various surfaces, sometimes intentionally, and are included in the intended scope of “contaminants,” for the purposes of this disclosure. Contaminants may take the form of liquids, droplets, films, or otherwise. With recent developments, including increasing areal density and reduced slider fly height and increased head precision, contamination (e.g., droplets) had not typically been problematic to a slider during HDD operation. With shrinking fly heights and head to disk clearance, present-day HDD sliders are increasingly more susceptible to contaminant droplet pick-up or other disturbances.
Contaminant build-up on a slider, once large enough, can lead to contaminants dripping or falling from the slider onto the disk surface, below. This dripping can form a contaminant concentration or “pool,” which may continue to grow and can cause a variety of problems. To reduce the likelihood of negative performance effects, the contaminants can be removed, dispersed, or cleaned from the slider surface using various contaminant actuation methods and structures. Contaminant actuation can occur prior to, during, or after substantial build-up of contaminants on a slider surface or disk surface below. However, existing methods for cleaning surfaces of a slider, especially a TE, each have significant drawbacks.
Several solutions have been proposed in the past for detection of contaminants (e.g., droplets) at the TE and for actuation or removal of the contaminants (e.g. dual-ended temperature coefficient of resistance [DETCR] and capacitance-based detection). Some examples of existing methods of removal include TE micro-channel, electrowetting, self-assembled monolayer (SAM) hydrophobic coatings, SAM patterning, among others.
Although some solutions exist for removal of TE contamination, the existing solutions suffer from various disadvantages and drawbacks. Some drawbacks include long times for removal of the contaminants (e.g. by electrowetting, SAM patterning, etc.), or risk of blocking channels (e.g., a TE micro-channel) for contaminant removal. In some existing cases, suspension of normal drive operation can be necessary for a duration that is long enough to remove the contaminants by external actuation. Once the drive operation is suspended, the contaminants can be removed with a fast seek-settle outside a read/write zone of a head, electrowetting on dielectric (EWOD)-based actuation, among other techniques.
Due to the nature of existing methods of contaminant sensing, noise and precision issues are often present, which can lead to undesirably low signal-to-noise ratios (SNRs) during contaminant sensing, which can have a negative impact on head read/write performance. One example cause of low SNR during sensing in the existing art can include temperature sensitivity of DETCR-based TE contaminant sensing, among others.
Thus, existing methods for removal of contaminants from various surfaces of a slider, such as the TE, suffer from drawbacks such as slow response times and undesirable suspension of operations during cleaning operations. Therefore, the problem of contamination and lubricant build-up on the TE of a slider has led to a need and desire for improved methods and systems for the removal of harmful contaminants from a slider surface without also correspondingly affecting HDD read/write operations.